Virtually all internal combustion engines on the market today utilize poppet type valves. FIGS. 1–4 illustrate schematically a single cylinder of a prior art internal combustion engine having typical poppet-type intake and exhaust valves installed therein. The poppet valve assembly 20 illustrated in FIGS. 1–4 typically resides in the head 22 of the internal combustion engine 2. Head 22 is bolted to the block 24 of the engine 2 immediately over cylinder 26. Piston 28 is slidably received within cylinder 26 in close fitting conformity therewith. The crank arm 30 is coupled between the piston head 28 and crankshaft 32, thereby translating the reciprocating, linear motion of the piston head 28 within the cylinder 26 into rotary motion about the axis of rotation of the crankshaft 32. The internal combustion engine 2 illustrated in FIGS. 1–4 is a four-stroke engine.
Poppet valves 34 have heads 36 that have cone shaped or beveled edges that mate with cooperating beveled edge of a valve seat 38 formed into the head 22. Poppet valve rods 40 extend rearwardly from the poppet valve heads 36 through valve guide bores 42 formed through the head 22. Poppet valves 34 are reciprocated longitudinally so as to selectively open and close an intake port 44 and an exhaust port 46 formed through the head 22. The poppet valves 34 are actuated between open and closed positions by a camshaft 48 having a plurality of cams 50 extending therefrom. As camshaft 48 rotates, the cams 50 strike lifters 52 which pivot so as to force poppet valve 34 into cylinder 26 thereby permitting fluidic communication with the interior of cylinder 2 through the ports 44, 46. It is to be understood that there exist many different variations on such an engine and that the prior art embodiment described in conjunction with FIGS. 1–4 is illustrative only.
Even from the schematic representations of the prior art poppet-type valve assembly 20 illustrated in FIGS. 1–4, it can be appreciated that a poppet valve assembly 20 is a very complicated structure. The costs associated with manufacturing, assembling, and maintaining such an assembly are quite high. Furthermore, the airflow characteristics associated with poppet valve assembles 20 are relatively inefficient as air, fuel, and combustion gases must enter or exist the cylinder 26 through a relatively small annular opening created between the poppet valve head 36 and valve seat 38 when the poppet valves 34 are opened. Therefore, entry of air or an air/fuel mixture into the cylinder at the beginning of an induction stroke of a four-stroke internal combustion engine may not be complete, and similarly, the flushing of combustion gases that takes place during the exhaust stroke may not be complete either. This situation typically results in less than ideal combustion within the cylinder 26.
Because of the tight tolerances necessary for a poppet-type valve assembly 20 to function properly, a great deal of care is required in both the manufacture and maintenance of the poppet valves 34. Because of the rigorous stresses to which poppet valves 34 are subjected, these valves may quickly wear, thereby degrading the seal that is formed between the beveled or cone shaped edges of the poppet valve head 36 and the valve seat 38. Furthermore, it is not uncommon for either the cone shaped edge of the poppet valve head 36 or the cooperating edge of the valve seat 38 to become pitted through use. In either case, the degree of compression that may be achieved within a cylinder 26 is lowered significantly.
Because a poppet-type valve assembly is such a complex mechanism, it is difficult to arrange an engine's components into a given engine compartment space. The arrangement of an engine's components is typically referred to as the “packaging” of the engine. The packaging of an engine may dictates the size and shape and also the location of the physical components thereof. The complexity and fragility of a poppet-type valve assembly 20 typically requires that the valve assembly 20 be readily accessible. Usually this means that the valve assembly 20 must be near the top of the engine 2. The difficulty in positioning the valve assembly 20 is further complicated by the need to provide cooling to the assembly. The engine block 24 and head 22 are typically cooled by running a coolant through passage such as passages 23. Such coolant passages 23 may not be able to sufficiently cool the valve assembly 20 when the engine 2 is under high stress. Subsequently, valve assemblies 20 may quickly become overheated and may become damaged.
Traditionally, internal combustion engines 2 using poppet-type valve assemblies 20 and particularly gasoline powered engines require the use of a carburetor or fuel injection system and mix and supply the requisite quantity of fuel and air so that the engine 2 may operate at a desired speed. These mechanisms are typically even more complex than the poppet valve 20 and correspondingly more expensive.
Accordingly, it is an object of the present invention to provide a rotary valve mechanism that is simple to manufacture and maintain, and that is also flexible enough to greatly simplify the packaging of the components of an engine. It is another object of the present invention to provide a rotary valve that increases the efficiency of air flow to and from a cylinder of an internal combustion engine and which allows for more complete combustion of the fuel supplied to the engine. Yet another object of the present invention is to provide a rotary valve that may incorporate a throttling mechanism that will obviate the need for a carburetor or fuel injection system as such. It is yet another object of this invention to provide a rotary valve assemble that may be easily constructed and arranged to simply replace a more complex poppet valve assembly.
These and other objectives and advantages of the invention will appear more fully from the following description, made in conjunction with the accompanying drawings wherein like reference characters refer to the same or similar parts throughout the several views.